Light emitting device and display device

ABSTRACT

A light emitting device comprises a light emitting substrate with a plurality of light emitting elements, and a luminance equalizer sheet provided opposite the light emitting substrate, having a plurality of through holes for transmitting light irradiated from the light emitting elements and having a linear expansion coefficient different from a linear expansion coefficient of the light emitting substrate, the light emitting substrate and the luminance equalizer sheet being positioned relative to each other at a predetermined position, at least one with a larger linear expansion coefficient among the light emitting substrate and the luminance equalizer sheet having a curved shape, and a degree of curvature of the one with the larger linear expansion coefficient being larger than a degree of curvature of one with a smaller linear expansion coefficient among the light emitting substrate and the luminance equalizer sheet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2020-098247 filed on Jun. 5, 2020. The entire disclosure of JapanesePatent Application No. 2020-098247 is hereby incorporated herein byreference.

BACKGROUND Field of the Invention

The present invention generally relates to a light emitting device and adisplay device. More specifically, the present invention relates to alight emitting device and a display device equipped with a lightemitting substrate having a light emitting element and a luminanceequalizer sheet.

Background Information

Some light emitting devices are equipped with a light emitting substratehaving a light emitting element and a luminance equalizer sheet (seeJapanese Patent Application Publication No. 2012-22977 (PatentLiterature 1), for example).

The light emitting device described in Patent Literature 1 above uses aluminance equalizer sheet with a plurality of through holes of differentsizes in order to obtain illumination light with uniform illuminancedistribution. In the light emitting device described in PatentLiterature 1 above, a metal material is used as the material of thelight emitting substrate, and an ultrafine-cellular foam lightreflection member is used as the material of the luminance equalizersheet.

SUMMARY

In order to obtain a uniform illuminance distribution, the relativepositional relationship between each light emitting element and thethrough hole pattern of the luminance equalizer sheet corresponding toeach light emitting element is important. Any misalignment in therelative positional relationship above will result in a decrease inluminance uniformity. Therefore, in order to suppress the misalignmentof the relative positional relationship above, a holding member isgenerally used to fix the relative positions of the light emittingelement and the luminance equalizer sheet.

In the light emitting device described in Patent Literature 1 above, asdescribed above, the materials of the light emitting substrate and theluminance equalizer sheet are different, and thus their respectivelinear expansion coefficients are also different. Therefore, the amountof expansion and contraction of the light emitting substrate due totemperature changes differs from the amount of expansion and contractionof the luminance equalizer sheet. When the light emitting substrate andthe luminance equalizer sheet expand or contract due to temperaturechanges, no misalignment occurs in the relative positional relationshipbetween each light emitting element and the through hole pattern of theluminance equalizer sheet corresponding to each light emitting elementat a positioning point (a fixed position) where the relative position isfixed. However, at a position away from the positioning point (the fixedposition) above, the difference in the linear expansion coefficients ofthe light emitting substrate and the luminance equalizer sheet causesthe misalignment in the relative positioning relationship above. Thismisalignment becomes larger the farther the position is away from thepositioning point (the fixed position) above, resulting in thedeterioration of luminance uniformity. In particular, light emittingdevices installed in vehicles have a large temperature fluctuationrange, and thus the deterioration of luminance uniformity caused bytemperature changes is unavoidable.

One object is to provide a light emitting device and a display devicethat can suppress deterioration of luminance uniformity caused bytemperature changes by reducing misalignment of the relative positionalrelationship of the light emitting substrate and the luminance equalizersheet caused by temperature changes.

In view of the state of the known technology and in accordance with afirst aspect of the present invention, a light emitting device accordingto the first aspect comprises a light emitting substrate with aplurality of light emitting elements, and a luminance equalizer sheetprovided opposite the light emitting substrate, having a plurality ofthrough holes for transmitting light irradiated from the light emittingelements and having a linear expansion coefficient different from alinear expansion coefficient of the light emitting substrate, the lightemitting substrate and the luminance equalizer sheet being positionedrelative to each other at a predetermined position, at least one with alarger linear expansion coefficient among the light emitting substrateand the luminance equalizer sheet having a curved shape, and a degree ofcurvature of the one with the larger linear expansion coefficient beinglarger than a degree of curvature of one with a smaller linear expansioncoefficient. Here, “a degree of curvature being small” of the presentdisclosure is a concept that includes not only being curved and havingsmall amount of curvature, but also being a non-curved flat surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is a cross-sectional view of a display device in accordance witha first embodiment;

FIG. 2 is a perspective view of a holding member of the display devicein accordance with the first embodiment;

FIG. 3 is a front elevational view of the holding member of the displaydevice in accordance with the first embodiment;

FIG. 4A is a schematic diagram showing a positional relationship betweena light emitting substrate and a luminance equalizer sheet at roomtemperature in a light emitting device in accordance with a comparativeexample;

FIG. 4B is a schematic diagram showing the positional relationshipbetween the light emitting substrate and the luminance equalizer sheetat high temperature in the light emitting device in accordance with thecomparative example;

FIG. 5A is a schematic diagram showing a positional relationship betweena light emitting substrate and a luminance equalizer sheet at roomtemperature in a light emitting device of the display device inaccordance with the first embodiment;

FIG. 5B is a schematic diagram showing the positional relationshipbetween the light emitting substrate and the luminance equalizer sheetat high temperature in the light emitting device of the display devicein accordance with the first embodiment;

FIG. 6 is a cross-sectional view of a display device in accordance witha second embodiment;

FIG. 7 is a cross-sectional view of a display device in accordance witha third embodiment;

FIG. 8 is a cross-sectional view of a display device in accordance witha fourth embodiment;

FIG. 9 is a cross-sectional view of a display device in accordance witha fifth embodiment;

FIG. 10 is a cross-sectional view of a display device in accordance witha sixth embodiment;

FIG. 11 is a cross-sectional view of a display device in accordance witha seventh embodiment;

FIG. 12 is an exploded perspective view of a first holding member and asecond holding member of a display device in accordance with an eighthembodiment;

FIG. 13 is a perspective view of a second holding member in accordancewith a ninth embodiment;

FIG. 14 is a cross-sectional view of the second holding member inaccordance with the ninth embodiment;

FIG. 15 is a perspective view of a second holding member in accordancewith a tenth embodiment; and

FIG. 16 is a cross-sectional view of the second holding member inaccordance with the tenth embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Selected embodiments will now be explained with reference to thedrawings. It will be apparent to those skilled in the art from thisdisclosure that the following descriptions of the embodiments areprovided for illustration only and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

In the present disclosure, the left-right direction or horizontaldirection as viewed from a front surface side of a display device isdescribed as an X direction. The up-down direction or vertical directionas viewed from the front surface side of the display device is describedas a Y direction. The direction extending between a rear surface sideand the front surface side of the display device is described as a Zdirection.

First Embodiment Configuration of Display Device

With reference to FIGS. 1 and 2, the configuration of a display device100 according to a first embodiment will be described.

As shown in FIG. 1, the display device 100 according to the firstembodiment is equipped with a light emitting device or backlight 1 and adisplay panel 2. FIG. 1 is a cross-sectional view of the display device100 taken along the X direction.

The light emitting device 1 has a light emitting substrate 11, areflective sheet 12, a luminance equalizer sheet (e.g., a luminanceuniformity sheet or a homogenizer) 13, a diffusion member or diffuser14, an optical sheet 15, and a holding member or casing 16. The lightemitting substrate 11, the reflective sheet 12, the luminance equalizersheet 13, the diffusion member 14 and the optical sheet 15 are arrangedin this order inside the holding member 16.

The light emitting substrate 11 is a printed wiring board and includes aplurality of light emitting elements 111 provided on a front surfaceside and a connector (not shown) to which power is supplied fromoutside. The light emitting substrate 11 has a flat (planar) shape. Thelight emitting substrate 11 includes a glass epoxy substrate using FR4(Flame Retardant 4), a glass composite substrate using CEM3 (CompositeEpoxy Material) 3), or a metal substrate, such as aluminum, but is notlimited to these. The linear expansion coefficient of the light emittingsubstrate 11 is smaller than the linear expansion coefficient of theluminance equalizer sheet 13.

The light emitting substrate 11 has a rectangular shape including foursides in plan view. A plurality of notches (not shown) are formed on apair of sides of the light emitting substrate 11 along the X directionand at least one of a pair of sides of the light emitting substrate 11along the Y direction, respectively, to engage with light emittingsubstrate engaging protrusions 164 (e.g., engaging protrusions) of theholding member 16, respectively (see FIG. 2). The light emittingsubstrate 11 is positioned in the X direction by the notches formed onthe pair of sides along the X direction and the corresponding lightemitting substrate engaging protrusions 164. The light emittingsubstrate 11 is positioned in the Y direction by the notch formed on theside along the Y direction and the corresponding light emittingsubstrate engaging protrusion 164. Thus, the light emitting substrate 11is fixed so as to be relatively positioned relative to the luminanceequalizer sheet 13 by the notches and the light emitting substrateengaging protrusions 164. As understood from FIG. 3, the notches formedon the pair of sides along the X direction are formed at center portionsof the pair of sides along the X direction corresponding to the lightemitting substrate engaging protrusions 164, but can be formed at pointsaway from the center portions corresponding to the light emittingsubstrate engaging protrusions 164.

The light emitting elements 111 are configured to emit light whenenergized. The light emitting elements 111 include an LED (LightEmitting Diode).

The reflective sheet 12 is disposed between the light emitting substrate11 and the luminance equalizer sheet 13 in the Z direction. Thereflective sheet 12 has a plurality of apertures 12 a through which thelight emitting elements 111 and their vicinities are exposed,respectively. The reflective sheet 12 is fixed to a surface of the lightemitting substrate 11 on which the light emitting elements 111 aremounted so as to avoid interfering with the light emitting elements 111by the apertures 12 a. The reflective sheet 12 is fixed to the lightemitting substrate 11 by a fixing method, such as double-sided tape. Thereflective sheet 12 is made of, but not limited to, polyethyleneterephthalate. The reflective sheet 12 increases the light utilizationefficiency by re-reflecting light that has been reflected by theluminance equalizer sheet 13, the diffusion member 14 or the opticalsheet 15 and returned to the light emitting substrate 11, and also makesthe luminance distribution uniform by making light advance from areasother than the light emitting elements 111 toward a light exit surfaceof the light emitting device 1.

The luminance equalizer sheet 13 is disposed between the reflectivesheet 12 and the diffusion member 14 in the Z direction. The luminanceequalizer sheet 13 is disposed spaced away at a distance of about 0.5 mmto 10 mm from the light emitting substrate 11. The luminance equalizersheet 13 has a plurality of through holes 131 (see FIG. 5) of differentsizes for transmitting the light irradiated from the light emittingelements 111. In the luminance equalizer sheet 13, some of the lightirradiated from the light emitting elements 111 is transmitted throughthe through holes 131, while other part of the light are reflected backtoward the light emitting substrate 11 in areas where the through holes131 are not formed. The luminance equalizer sheet 13 is designed byconsidering the size of the through holes 131, the number of the throughholes 131 and the arrangement of the through holes 131 corresponding tothe light emitting elements 111 so that the luminance in a lightemitting surface or front surface of the light emitting device 1 is madeuniform. The luminance equalizer sheet 13 is formed, for example, suchthat the through holes 131 that have a plurality of different sizes,ranging from about 0.2 mm to 2 mm, are densely arranged at intervals ofabout 0.2 mm. By using this luminance equalizer sheet 13, the reflectionof light is repeated between the reflective sheet 12 on the lightemitting substrate 11 and the luminance equalizer sheet 13, and theluminance uniformity can be improved.

The luminance equalizer sheet 13 has a rectangular shape including foursides in plan view. A plurality of notches (not shown) is formed on apair of sides of the luminance equalizer sheet 13 along the X directionand at least one of a pair of sides of the luminance equalizer sheet 13along the Y direction, respectively, to engage with luminance equalizersheet engaging protrusions 165 (e.g., engaging protrusions) of theholding member 16, respectively, (see FIG. 2). The luminance equalizersheet 13 is positioned in the X direction by the notches formed on thepair of sides along the X direction and the corresponding luminanceequalizer sheet engaging protrusions 165. The luminance equalizer sheet13 is positioned in the Y direction by the notch formed on the sidealong the Y direction and the corresponding luminance equalizer sheetengaging protrusion 165. Thus, the luminance equalizer sheet 13 is fixedso as to be relatively positioned relative to the light emittingsubstrate 11 by the notches and the luminance equalizer sheet engagingprotrusions 165. As understood from FIG. 3, the notches formed on thepair of sides along the X direction are formed at center portions of thepair of sides along the X direction corresponding to the luminanceequalizer sheet engaging protrusions 165, but can be formed or at pointsaway from the center portions corresponding to the luminance equalizersheet engaging protrusions 165.

The luminance equalizer sheet 13 is made of, but not limited to,polyethylene terephthalate. The linear expansion coefficient of theluminance equalizer sheet 13 is larger than the linear expansioncoefficient of the light emitting substrate 11. Thus, in the illustratedembodiment, the luminance equalizer sheet 13 is made of a differentmaterial from the light emitting substrate 11.

As shown in FIG. 1, the luminance equalizer sheet 13 has a curved shape.Specifically, the luminance equalizer sheet 13 has a single curvedshape. More specifically, the luminance equalizer sheet 13 has a curvedcross sectional shape in the cross section of the display device 100taken along the X direction or a ZX plane (FIG. 1), while the luminanceequalizer sheet 13 has a flat cross sectional shape in the cross sectionof the display device 100 taken along the Y direction or a YZ plane. Inparticular, in the illustrated embodiment, the luminance equalizer sheet13 has a curved shape that is convex toward the light emitting substrate11 in the cross section of the display device 100 taken along the Xdirection. The luminance equalizer sheet 13 is curved so that an angleθ1 between a plane P1 of the light emitting substrate 11 and a tangentplane TP1 of the luminance equalizer sheet 13 in a perpendiculardirection of the plane P1 of the light emitting substrate 11 increasesas moving away from a positioning position where the notch is formed.Specifically, the luminance equalizer sheet 13 is curved so that theangle θ1 between the plane P1 of the light emitting substrate 11 (i.e.,a tangent plane of the light emitting substrate 11 at a position of thelight emitting substrate 11) and the tangent plane TP1 of the luminanceequalizer sheet 13 at a position of the luminance equalizer sheet 13that is located in the perpendicular direction of the plane P1 of thelight emitting substrate 11 relative to the position of the lightemitting substrate 11 increases as the position of the light emittingsubstrate 11 moving away from the positioning position where the notchis formed. In the illustrated embodiment, the notches of the lightemitting substrate 11 are formed at the center portions of the pair ofsides along the X direction, while the notches of the luminanceequalizer sheet 13 are formed at the center portions of the pair ofsides along the X direction. Thus, as shown in FIG. 1, the angle θ1monotonically increases as moving outward in the X direction relative toa longitudinal center plane of the display device 100 that is a YZ planeand extends through the notches of the light emitting substrate 11 andthe notches of the luminance equalizer sheet 13.

The positioning position where the notch of the luminance equalizersheet 13 is formed is located at a position where a plane orthogonal tothe tangent plane TP1 of the luminance equalizer sheet 13 and a planeorthogonal to the plane P1 of the light emitting substrate 11 overlapeach other. Specifically, in this embodiment, the positioning positionof the luminance equalizer sheet 13 is provided at the top of the curvedshape of the luminance equalizer sheet 13, and the positioning positionof the light emitting substrate 11 is provided at a portion located inthe perpendicular direction or Z direction from this top. Morespecifically, as shown in FIG. 1, the plane orthogonal to the tangentplane TP1 of the luminance equalizer sheet 13 at the center portions ofthe pair of sides of the luminance equalizer sheet 13 along the Xdirection (at the positioning position of the luminance equalizer sheet13) matches with the plane orthogonal to the plane P1 of the lightemitting substrate 11 at the center portions of the pair of sides of thelight emitting substrate 11 (at the positioning position of the lightemitting substrate 11), which also matches with the longitudinal centerplane of the display device 100 that is a YZ plane and extends throughthe notches of the light emitting substrate 11 and the notches of theluminance equalizer sheet 13.

The diffusion member 14 is disposed between the luminance equalizersheet 13 and the optical sheet 15. The diffusion member 14 is made ofpolycarbonate, for example. As shown in FIG. 1, the diffusion member 14is formed of a plate member molded into a curved shape that is convextoward the luminance equalizer sheet 13 in the cross section of thedisplay device 100 taken along the X direction. The curved shape of thediffusion member 14 is a curved shape corresponding to the curved shapeof the luminance equalizer sheet 13. The curved shape of the diffusionmember 14 is a curved shape extending along a curved holding portion 163(see FIG. 2) of the holding member 16 described later. Along the curvedshape of the diffusion member 14, the luminance equalizer sheet 13 hasthe curved shape that is convex toward the light emitting substrate 11.The diffusion member 14 may be formed of a sheet member. The diffusionmember 14 diffuses the light that passes through the luminance equalizersheet 13 and enters the diffusion member 14, and can also guide thelight to the point where the through holes 131 are not formed on thefront surface side of the luminance equalizer sheet 13.

The optical sheet 15 is disposed between the diffusion member 14 and thedisplay panel 2. The optical sheet 15 includes, for example, a prismsheet 151 to increase the light utilization efficiency of the lightemitting device 1, and a polarization control sheet 152 to increase thelight utilization efficiency of the display panel 2. The optical sheet15 may further include a viewing angle control sheet that narrows theviewing angle of the display device 100. The curved shape of the opticalsheet 15 is a curved shape that corresponds to the curved shape of theluminance equalizer sheet 13.

As shown in FIGS. 2 and 3, the holding member 16 is a box shape with anopening on the front surface side and has a bottom portion 161 and fourside portions 162. The light emitting substrate 11 is disposed on thebottom portion 161. The light emitting substrate 11 is fixed to thebottom portion 161 by a fixing method such as double-sided tape. Sincethe light emitting substrate 11 generates heat, the double-sided tape isselected by considering heat transfer properties. On the front surfaceside of the light emitting substrate 11 on the bottom portion 161, thereflective sheet 12, the luminance equalizer sheet 13, the diffusionmember 14 and the optical sheet 15 are arranged in this order. The sideportions 162 form four side walls of the box-shaped holding member 16.The side portions 162 restrict the positions of the light emittingsubstrate 11, the reflective sheet 12, the luminance equalizer sheet 13,the diffusion member 14 and the optical sheet 15, and also prevent lightfrom leaking and foreign matter from entering. The side portions 162have a curved holding portion 163 that protrudes inward between thelight emitting substrate 11 and the luminance equalizer sheet 13 and isformed in a curved shape that is convex toward the light emittingsubstrate 11 at the side portions 162 along the X direction and a flatshape at the side portions 162 along the Y direction. The curved holdingportion 163 forms a step that supports the periphery of the luminanceequalizer sheet 13 and holds the curved shape of the luminance equalizersheet 13. The curved holding portion 163 holds the luminance equalizersheet 13 between itself and the diffusion member 14. The side portions162 fix the diffusion member 14 and the optical sheet 15 using tape andthe like.

As shown in FIGS. 2 and 3, the bottom portion 161 has the light emittingsubstrate engaging protrusions 164 for engaging with the notches of thelight emitting substrate 11. Specifically, in the illustratedembodiment, the bottom portion 161 has the light emitting substrateengaging protrusions 164 that protrude inward from the pair of the sideportions 162 along the X direction and at least one side portion of thepair of the side portions 162 along the Y direction.

As shown in FIGS. 2 and 3, the curved holding portion 163 includes apair of curved sections extending along the X direction and a pair offlat sections extending along the Y direction. The curved sections ofthe curved holding portion 163 has a curved shape as viewed in the Ydirection that corresponds to the curved shape of the luminanceequalizer sheet 13. The flat sections of the curved holding portion 163has a flat shape as viewed in the X direction. The curved holdingportion 163 has the luminance equalizer sheet engaging protrusions 165for engaging with the notches of the luminance equalizer sheet 13.Specifically, in the illustrated embodiment, the curved holding portion163 has the luminance equalizer sheet engaging protrusions 165 on thepair of the curved sections of the curved holding portion 163 along theX direction and at least one of the pair of the flat sections of thecurved holding portion 163 along the Y direction, as shown in FIGS. 2and 3. In particular, in the illustrated embodiment, as shown in FIG. 3,the luminance equalizer sheet engaging protrusions 165 on the curvedsections of the curved holding portion 163 protrude inward from the sideportions 162 along the X direction, respectively, and the luminanceequalizer sheet engaging protrusion 165 on one of the flat sections ofthe curved holding portion 163 protrude inward from the side portion 162along the Y direction.

The holding member 16 positions the light emitting substrate 11 by thelight emitting substrate engaging protrusions 164 that definepositioning positions of the light emitting substrate 11, respectively.The holding member 16 positions the luminance equalizer sheet 13 by theluminance equalizer sheet engaging protrusions 165 that definepositioning positions of the luminance equalizer sheet 13, respectively.The holding member 16 fixes the light emitting substrate 11 and theluminance equalizer sheet 13 so that the light emitting substrate 11 andthe luminance equalizer sheet 13 can be relatively positioned. Theluminance equalizer sheet engaging protrusions 165 are arranged at aposition where a tangent plane of the curved holding portion 163 alongthe X direction is parallel to the bottom portion 161 of the holdingmember 16. The luminance equalizer sheet engaging protrusions 165 formedon the pair of the curved sections of the curved holding portion 163along the X direction can be formed at the center portions of this pairof the curved sections of the curved holding portion 163, or can beformed at points away from the center portions. The light emittingsubstrate engaging protrusions 164 are provided in the portions locatedin the perpendicular direction or Z direction from the luminanceequalizer sheet engaging protrusions 165, respectively. The lightemitting substrate engaging protrusions 164 formed on the pair of theside portions 162 along the X direction can be formed at the centerportions of this pair of the side portions 162, or can be formed atpoints away from the center portions. The reflective sheet 12 is alsoprovided with notches (not shown) that can share the light emittingsubstrate engaging protrusions 164 of the holding member 16 with thenotches of the light emitting substrate 11, and is fixed to bepositioned with respect to the light emitting element 111 of the lightemitting substrate 11.

The display panel 2 is disposed on the optical sheet 15 of the lightemitting device 1. The display panel 2 is fixed near the opening of theholding member 16. The display panel 2 is fixed to the holding member 16using double-sided tape or other fixing means. The display panel 2 is aliquid crystal panel. The display panel 2 has a plurality of pixels, anddisplays an image by each of the pixels transmitting or absorbing lightfrom the light emitting device 1 depending on the applied voltage. Thedisplay panel 2 has a curved shape that is convex toward the lightemitting substrate 11. In the first embodiment, the luminance equalizersheet 13, the diffusion member 14, the optical sheet 15 and the curvedholding portion 163 of the holding member 16 are curved along thedisplay panel 2.

Effect of First Embodiment

The following effects can be obtained with the first embodiment.

In the first embodiment, as described above, the luminance equalizersheet 13, which has the linear expansion coefficient larger than thelinear expansion coefficient of the light emitting substrate 11, has thecurved shape, and the degree of curvature of the luminance equalizersheet 13, which has the larger linear expansion coefficient, is largerthan the degree of curvature of the light emitting substrate 11, whichhas the smaller linear expansion coefficient. By making the luminanceequalizer sheet 13 with the larger linear expansion coefficient morecurved, the positional shift amount of the luminance equalizer sheet 13with the larger linear expansion coefficient relative to the lightemitting substrate 11 with the smaller linear expansion coefficient canbe reduced at a position away from the predetermined position. In otherwords, if the positional shift direction caused by the expansion of thelight emitting substrate 11, which has the smaller linear expansioncoefficient, is the reference direction, then the luminance equalizersheet 13, which has the larger linear expansion coefficient, expands inthe direction inclined to the reference direction due to the curvature.As a result, the expansion of the luminance equalizer sheet 13, whichhas the larger linear expansion coefficient, includes the orthogonaldirection component in the direction orthogonal to the referencedirection, in addition to the reference direction componentcorresponding to the positional shift. The positional shift (thereference direction component) can be reduced by the amount of thisorthogonal direction component caused by the curvature. With thisconfiguration, deterioration of luminance uniformity caused bytemperature changes can be suppressed by reducing misalignment of therelative positional relationship of the light emitting substrate 11 andthe luminance equalizer sheet 13 caused by temperature changes.

Here, referring to FIGS. 4A, 4B, 5A and 5B, the positional relationshipbetween a light emitting substrate and a luminance equalizer sheet in acomparative example and this embodiment at room temperature and at hightemperature. In FIGS. 4A, 4B, 5A and 5B, the light emitting substrateand the luminance equalizer sheet are fixed so as to be relativelypositioned with each other via the holding member not shown in thedrawings. FIGS. 4A and 4B show the comparative example pertaining to theconfiguration of a light emitting substrate 91 and a luminance equalizersheet 93 in a light emitting device, and the light emitting substrate91, which has a flat shape, and the luminance equalizer sheet 93, whichhas a larger linear expansion coefficient than the light emittingsubstrate 91 and has a flat shape, are arranged in parallel relative toeach other. In the comparative example, as shown in FIG. 4A, at roomtemperature, a light emitting element 911 on the light emittingsubstrate 91 and a plurality of through holes 931 on the luminanceequalizer sheet 93 corresponding to the light emitting element 911 arearranged relative to each other in correct positions as designed, andthus the light emitting device can be said to have high luminanceuniformity. However, when the temperature changes from room temperatureto high temperature, for example, the light emitting substrate 91 andthe luminance equalizer sheet 93 expand. In this case, as shown in FIG.4B, at a position away from a positioning position (or a fixedposition), the amount of expansion of the luminance equalizer sheet 93on which the plurality of through holes 931 corresponding to the lightemitting elements 911 are disposed is larger than the amount ofexpansion of the light emitting substrate 91 on which the light emittingelements 911 corresponding to the plurality of through holes 931 aredisposed. Since the light emitting elements 911 on the light emittingsubstrate 91 and the corresponding plurality of through holes 931 on theluminance equalizer sheet 93 are arranged in parallel to each other, thedifference in the amount of expansion due to the difference in thelinear expansion coefficients of the light emitting substrate 91 and theluminance equalizer sheet 931 directly becomes a relative positionalshift, which results in a decrease in luminance uniformity.

In contrast, FIGS. 5A and 5B show an example of the configuration of thelight emitting substrate 11 and the luminance equalizer sheet 13 in thelight emitting device 1 according to the first embodiment, and the lightemitting substrate 11 having a flat shape and the luminance equalizersheet 13 having a larger linear expansion coefficient than the lightemitting substrate 11 and having a curved shape are arranged oppositerelative to each other. In the configuration of the first embodiment, asshown in FIG. 5A, at room temperature, the light emitting element 111 onthe light emitting substrate 11 and the plurality of through holes 131on the luminance equalizer sheet 13 corresponding to the light emittingelement 111 can be arranged relative to each other in correct positionsas designed, and the light emitting device 1 with high luminanceuniformity can be realized. Furthermore, when the temperature changesfrom room temperature to high temperature and the light emittingsubstrate 11 and the luminance equalizer sheet 13 expand, as shown inFIG. 5B, at a position away from the positioning position, the amount ofexpansion of the luminance equalizer sheet 13 on which the plurality ofthrough holes 131 corresponding to the light emitting elements 111 aredisposed is larger than the amount of expansion of the light emittingsubstrate 11 on which the light emitting element 111 corresponding tothe plurality of through holes 131 are disposed. However, the luminanceequalizer sheet 13, which has a larger linear expansion coefficient,expands in a direction inclined to the reference direction due tocurvature. As a result, the expansion of the one with the larger linearexpansion coefficient (i.e., the luminance equalizer sheet 13 in thefirst embodiment) includes an orthogonal direction component in adirection orthogonal to the reference direction, in addition to thereference direction component corresponding to the positional shift. Thepositional shift (the reference direction component) can be reduced bythe amount of this orthogonal direction component caused by thecurvature. Therefore, it is possible to suppress misalignment of therelative positional relationship between each light emitting element 111of the light emitting substrate 11 and each pattern of the through holes131 of the luminance equalizer sheet 13 corresponding to each lightemitting element 111 at a position away from the positioning position.As a result, the deterioration of luminance uniformity can besuppressed.

The farther away from the positioning position, the larger thepositional shift amount due to expansion. In the first embodiment, asdescribed above, the light emitting substrate 11 and the luminanceequalizer sheet 13 are designed so that the luminance equalizer sheet 13is curved such that the angle θ1 between the plane P1 of the lightemitting substrate 11 and the tangent plane TP1 of the luminanceequalizer sheet 13 in the perpendicular direction of the plane P1 of thelight emitting substrate 11 increases as moving away from thepositioning position. With this configuration, the amount of theorthogonal direction component generated can be increased as moving awayfrom the predetermined position, and thus an amount of decrease in thereference direction component can be increased as moving away from thepredetermined position. With this configuration, the deterioration ofluminance uniformity caused by temperature changes can be furthersuppressed by further reducing misalignment of the relative positionalrelationship of the light emitting substrate 11 and the luminanceequalizer sheet 13 caused by temperature changes.

In the first embodiment, as described above, the positioning position isthe position where the plane orthogonal to the tangent plane of theluminance equalizer sheet 13, which has the larger linear expansioncoefficient, overlaps the plane orthogonal to the plane of the lightemitting substrate 11, which has the smaller linear expansioncoefficient. With this configuration, since the light emitting substrate11 having a flat shape and the luminance equalizer sheet 13 having acurved shape can be stably fixed at the positioning position, theassemblability of the luminance equalizer sheet 13 can be improved.

In the first embodiment, as described above, the luminance equalizersheet 13 has a curved shape, and the diffusion member 14 is furthercomprised that is disposed on the opposite side of the luminanceequalizer sheet 13 from the light emitting substrate 11 and has a curvedshape corresponding to the curved shape of the luminance equalizer sheet13. With this configuration, the degree of curvature of the luminanceequalizer sheet 13, which has the curved shape, can be appropriatelymaintained. Therefore, the deterioration of luminance uniformity causedby temperature changes can be suppressed.

In the first embodiment, as described above, the optical sheet 15 isfurther comprised that is disposed on the opposite side of the diffusionmember 14 from the luminance equalizer sheet 13 and has a curved shapecorresponding to the curved shape of the luminance equalizer sheet 13.With this configuration, the degree of curvature of the luminanceequalizer sheet 13, which has the curved shape, can be moreappropriately maintained. Therefore, the deterioration of luminanceuniformity caused by temperature changes can be suppressed.

In the first embodiment, as described above, the luminance equalizersheet 13 has a curved shape, the holding member 16 is further comprisedthat holds the light emitting substrate 11 and the luminance equalizersheet 13, and the holding member 16 has the curved holding portion 163having a curved shape for holding the curvature of the luminanceequalizer sheet 13. With this configuration, the luminance equalizersheet 13 with the desired curved shape can be configured simply byplacing the luminance equalizer sheet 13 formed by a flexible sheet onthe curved holding portion 163.

Second Embodiment

Referring to FIG. 6, the configuration of a display device 200 accordingto a second embodiment will be explained. In view of the similaritybetween the first and second embodiments, the parts of the secondembodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the secondembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the second embodiment, unlike the first embodiment, the lightemitting substrate 11 and the luminance equalizer sheet 13 each have acurved shape. Specifically, in the illustrated embodiment, the lightemitting substrate 11 and the luminance equalizer sheet 13 each have asingle curved shape. In particular, in the illustrated embodiment, theluminance equalizer sheet 13, which has a linear expansion coefficientlarger than a linear expansion coefficient of the light emittingsubstrate 11, has a curved shape that is convex toward the lightemitting substrate 11, the light emitting substrate 11 has a curvedshape that is concave away from the luminance equalizer sheet 13, andthe degree of curvature of the luminance equalizer sheet 13 isconfigured to be larger than the degree of curvature of the lightemitting substrate 11. The bottom portion 161 of the holding member 16has a curved shape that is concave away from the light emittingsubstrate 11 in the cross section of the display device 200 taken alongthe X direction. The light emitting substrate 11 and the luminanceequalizer sheet 13 are curved with respect to each other so that anangle θ2 between a tangent plane TP2 a of the light emitting substrate11 and a tangent plane TP2 b of the luminance equalizer sheet 13 in theperpendicular direction of the tangent plane TP2 a of the light emittingsubstrate 11 increases as moving away from the positioning position.Specifically, the light emitting substrate 11 and the luminanceequalizer sheet 13 are curved with respect to each other so that theangle θ2 between the tangent plane TP2 a of the light emitting substrate11 at a position of the light emitting substrate 11 and the tangentplane TP2 b of the luminance equalizer sheet 13 at a position of theluminance equalizer sheet 13 located in the perpendicular direction ofthe tangent plane TP2 a of the light emitting substrate 11 relative tothe position of the light emitting substrate 11 increases as theposition of the light emitting substrate 11 moving away from thepositioning position. More specifically, in the illustrated embodiment,the angle θ2 monotonically increases as moving outward in the Xdirection relative to a longitudinal center plane of the display device200 that is a YZ plane and extends through the positioning positions ornotches of the light emitting substrate 11 and the luminance equalizersheet 13.

The other configuration of the second embodiment is the same as thefirst embodiment above.

Effect of Second Embodiment

In the second embodiment, as described above, the luminance equalizersheet 13, which has the linear expansion coefficient larger than thelinear expansion coefficient of the light emitting substrate 11, has acurved shape that is convex toward the light emitting substrate 11, thelight emitting substrate 11 has a curved shape that is concave away fromthe luminance equalizer sheet 13, and the degree of curvature of theluminance equalizer sheet 13 is configured to be larger than the degreeof curvature of the light emitting substrate 11. With thisconfiguration, as in the first embodiment above, deterioration ofluminance uniformity caused by temperature changes can be suppressed byreducing misalignment of the relative positional relationship of thelight emitting substrate 11 and the luminance equalizer sheet 13 causedby temperature changes.

If the light emitting substrate 11 having the curved shape expands andcontracts along the bottom portion 161 of the holding member 16 due totemperature changes, the direction of the light emitting elements 111will change. However, for example, if the curvature amount of the lightemitting substrate 11 is about R800 mm to R3000 mm, the shift amount dueto expansion and contraction is less than 1 mm. Therefore, the amount ofchange in the direction of the light emitting elements 111 is very smalland the angular distribution of the light intensity hardly changes.Therefore, even if the light emitting substrate 11 has a curved shape,the effect of changing the direction of the light emitting elements 111can be ignored.

The other effects of the second embodiment are the same as the firstembodiment.

Third Embodiment

Referring to FIG. 7, the configuration of a display device 300 accordingto a third embodiment will be explained. In view of the similaritybetween the first and third embodiments, the parts of the thirdembodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the thirdembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the third embodiment, unlike the first embodiment, the light emittingsubstrate 11 and the luminance equalizer sheet 13 each have a curvedshape. Specifically, in the illustrated embodiment, the light emittingsubstrate 11 and the luminance equalizer sheet 13 each have a singlecurved shape. In particular, in the illustrated embodiment, theluminance equalizer sheet 13, which has a linear expansion coefficientlarger than a linear expansion coefficient of the light emittingsubstrate 11, has a curved shape that is concave away from the lightemitting substrate 11, the light emitting substrate 11 has a curvedshape that is convex toward the luminance equalizer sheet 13, and thedegree of curvature of the luminance equalizer sheet 13 is configured tobe larger than the degree of curvature of the light emitting substrate11. The bottom portion 161 of the holding member 16 has a curved shapethat is convex toward the light emitting substrate 11 in the crosssection of the display device 300 taken along the X direction. Thediffusion member 14, the optical sheet 15, the curved holding portion163 along the X direction of the holding member 16, and the displaypanel 2 are curved along the luminance equalizer sheet 13 in the crosssection of the display device 300 taken along the X direction. The lightemitting substrate 11 and the luminance equalizer sheet 13 are curvedwith respect to each other so that an angle θ3 between a tangent planeTP3 a of the light emitting substrate 11 and a tangent plane TP3 b ofthe luminance equalizer sheet 13 in the perpendicular direction of thetangent plane TP3 a of the light emitting substrate 11 increases asmoving away from the positioning position. Specifically, the lightemitting substrate 11 and the luminance equalizer sheet 13 are curvedwith respect to each other so that the angle θ3 between the tangentplane TP3 a of the light emitting substrate 11 at a position of thelight emitting substrate 11 and the tangent plane TP3 b of the luminanceequalizer sheet 13 at a position of the luminance equalizer sheet 13located in the perpendicular direction of the tangent plane TP3 a of thelight emitting substrate 11 relative to the position of the lightemitting substrate 11 increases as the position of the light emittingsubstrate 11 moving away from the positioning position. Morespecifically, in the illustrated embodiment, the angle θ3 monotonicallyincreases as moving outward in the X direction relative to alongitudinal center plane of the display device 300 that is a YZ planeand extends through the positioning positions or notches of the lightemitting substrate 11 and the luminance equalizer sheet 13.

The other configuration of the third embodiment is the same as the firstembodiment above.

Effect of Third Embodiment

In the third embodiment, as described above, the luminance equalizersheet 13, which has the linear expansion coefficient larger than thelinear expansion coefficient of the light emitting substrate 11, has acurved shape that is concave away from the light emitting substrate 11,the light emitting substrate 11 has a curved shape that is convex towardthe luminance equalizer sheet 13, and the degree of curvature of theluminance equalizer sheet 13 is configured to be larger than the degreeof curvature of the light emitting substrate 11. With thisconfiguration, as in the first embodiment above, deterioration ofluminance uniformity caused by temperature changes can be suppressed byreducing misalignment of the relative positional relationship of thelight emitting substrate 11 and the luminance equalizer sheet 13 causedby temperature changes.

The other effects of the third embodiment are the same as the firstembodiment.

In the third embodiment, alternatively, the luminance equalizer sheet13, which has the linear expansion coefficient larger than the linearexpansion coefficient of the light emitting substrate 11, can have thecurved shape that is concave away from the light emitting substrate 11,the light emitting substrate 11 can have a flat shape or a curved shapethat is concave away from the luminance equalizer sheet 13, and thedegree of curvature of the luminance equalizer sheet 13 can be largerthan the degree of curvature of the light emitting substrate 11.

Fourth Embodiment

Referring to FIG. 8, the configuration of a display device 400 accordingto a fourth embodiment will be explained. In view of the similaritybetween the first and fourth embodiments, the parts of the fourthembodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the fourthembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the fourth embodiment, unlike the first embodiment, the lightemitting substrate 11 and the luminance equalizer sheet 13 each have acurved shape. Specifically, in the illustrated embodiment, the lightemitting substrate 11 and the luminance equalizer sheet 13 each have asingle curved shape. In particular, in the illustrated embodiment, theluminance equalizer sheet 13, which has a linear expansion coefficientsmaller than a linear expansion coefficient of the light emittingsubstrate 11, has a curved shape that is convex toward the lightemitting substrate 11, the light emitting substrate 11 has a curvedshape that is concave away from the luminance equalizer sheet 13, andthe degree of curvature of the luminance equalizer sheet 13 isconfigured to be smaller than the degree of curvature of the lightemitting substrate 11. The bottom portion 161 of the holding member 16has a curved shape that is concave away from the light emittingsubstrate 11 in the cross section of the display device 400 taken alongthe X direction. The light emitting substrate 11 and the luminanceequalizer sheet 13 are curved with respect to each other so that anangle θ4 between a tangent plane TP4 a of the light emitting substrate11 and a tangent plane TP4 b of the luminance equalizer sheet 13 in theperpendicular direction of the tangent plane TP4 a of the light emittingsubstrate 11 increases as moving away from the positioning position.Specifically, the light emitting substrate 11 and the luminanceequalizer sheet 13 are curved with respect to each other so that theangle θ4 between the tangent plane TP4 a of the light emitting substrate11 at a position of the light emitting substrate 11 and the tangentplane TP4 b of the luminance equalizer sheet 13 at a position of theluminance equalizer sheet 13 located in the perpendicular direction ofthe tangent plane TP4 a of the light emitting substrate 11 relative tothe position of the light emitting substrate 11 increases as theposition of the light emitting substrate 11 moving away from thepositioning position. More specifically, in the illustrated embodiment,the angle θ4 monotonically increases as moving outward in the Xdirection relative to a longitudinal center plane of the display device400 that is a YZ plane and extends through the positioning positions ornotches of the light emitting substrate 11 and the luminance equalizersheet 13. In this embodiment, the materials of the luminance equalizersheet 13 and the light emitting substrate 11 are not particularlylimited as long as the linear expansion coefficient of the luminanceequalizer sheet 13 is smaller than the linear expansion coefficient ofthe light emitting substrate 11.

The other configurations of the fourth embodiment are the same as thefirst embodiment above.

Effect of Fourth Embodiment

In the fourth embodiment, as described above, the luminance equalizersheet 13, which has the linear expansion coefficient smaller than thelinear expansion coefficient of the light emitting substrate 11, has acurved shape that is convex toward the light emitting substrate 11, thelight emitting substrate 11 has a curved shape that is concave away fromthe luminance equalizer sheet 13, and the degree of curvature of theluminance equalizer sheet 13 is configured to be smaller than the degreeof curvature of the light emitting substrate 11. With thisconfiguration, as in the first embodiment above, deterioration ofluminance uniformity caused by temperature changes can be suppressed byreducing misalignment of the relative positional relationship of thelight emitting substrate 11 and the luminance equalizer sheet 13 causedby temperature changes.

The other effects of the fourth embodiment are the same as those of thefirst embodiment.

In the fourth embodiment, alternatively, the luminance equalizer sheet13, which has the linear expansion coefficient smaller than the linearexpansion coefficient of the light emitting substrate 11, can have thecurved shape that is convex toward the light emitting substrate 11, thelight emitting substrate 11 can have a curved shape that is convextoward the luminance equalizer sheet 13, and the degree of curvature ofthe luminance equalizer sheet 13 can be smaller than the degree ofcurvature of the light emitting substrate 11.

Fifth Embodiment

Referring to FIG. 9, the configuration of a display device 500 accordingto a fifth embodiment will be explained. In view of the similaritybetween the first and fifth embodiments, the parts of the fifthembodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the fifthembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the fifth embodiment, unlike the first embodiment, the light emittingsubstrate 11 and the luminance equalizer sheet 13 each have a curvedshape. Specifically, in the illustrated embodiment, the light emittingsubstrate 11 and the luminance equalizer sheet 13 each have a singlecurved shape. In particular, in the illustrated embodiment, theluminance equalizer sheet 13, which has a linear expansion coefficientsmaller than a linear expansion coefficient of the light emittingsubstrate 11, has a curved shape that is concave away from the lightemitting substrate 11, the light emitting substrate 11 has a curvedshape that is convex toward the luminance equalizer sheet 13, and thedegree of curvature of the luminance equalizer sheet 13 is configured tobe smaller than the degree of curvature of the light emitting substrate11. The bottom portion 161 of the holding member 16 has a curved shapethat is convex toward the light emitting substrate 11 in the crosssection of the display device 500 taken along the X direction. Thediffusion member 14, the optical sheet 15, the curved holding portion163 along the X direction of the holding member 16, and the displaypanel 2 are curved along the luminance equalizer sheet 13 in the crosssection of the display device 500 taken along the X direction. The lightemitting substrate 11 and the luminance equalizer sheet 13 are designedso that the light emitting substrate 11 is curved so that an angle θ5between a tangent plane TP5 a of the light emitting substrate 11 and atangent plane TP5 b of the luminance equalizer sheet 13 in theperpendicular direction of the tangent plane TP5 a of the light emittingsubstrate 11 increases as moving away from the positioning position.Specifically, the light emitting substrate 11 and the luminanceequalizer sheet 13 are curved with respect to each other so that theangle θ5 between the tangent plane TP5 a of the light emitting substrate11 at a position of the light emitting substrate 11 and the tangentplane TP5 b of the luminance equalizer sheet 13 at a position of theluminance equalizer sheet 13 located in the perpendicular direction ofthe tangent plane TP5 a of the light emitting substrate 11 relative tothe position of the light emitting substrate 11 increases as theposition of the light emitting substrate 11 moving away from thepositioning position. More specifically, in the illustrated embodiment,the angle θ5 monotonically increases as moving outward in the Xdirection relative to a longitudinal center plane of the display device500 that is a YZ plane and extends through the positioning positions ornotches of the light emitting substrate 11 and the luminance equalizersheet 13. In this embodiment, the materials of the luminance equalizersheet 13 and the light emitting substrate 11 are not particularlylimited as long as the linear expansion coefficient of the luminanceequalizer sheet 13 is smaller than the linear expansion coefficient ofthe light emitting substrate 11.

The other configuration of the fifth embodiment is the same as the firstembodiment above.

Effect of Fifth Embodiment

In the fifth embodiment, as described above, the luminance equalizersheet 13, which has the linear expansion coefficient smaller than thelinear expansion coefficient of the light emitting substrate 11, has acurved shape that is concave away from the light emitting substrate 11,the light emitting substrate 11 has a curved shape that is convex towardthe luminance equalizer sheet 13, and the degree of curvature of theluminance equalizer sheet 13 is configured to be smaller than the degreeof curvature of the light emitting substrate 11. With thisconfiguration, as in the first embodiment above, deterioration ofluminance uniformity caused by temperature changes can be suppressed byreducing misalignment of the relative positional relationship of thelight emitting substrate 11 and the luminance equalizer sheet 13 causedby temperature changes.

The other effects of the fifth embodiment are the same as those of thefirst embodiment.

In the fifth embodiment, alternatively, the luminance equalizer sheet13, which has the linear expansion coefficient smaller than the linearexpansion coefficient of the light emitting substrate 11, can have thecurved shape that is concave away from the light emitting substrate 11,the light emitting substrate 11 can have a curved shape that is concaveaway from the luminance equalizer sheet 13, and the degree of curvatureof the luminance equalizer sheet 13 can be smaller than the degree ofcurvature of the light emitting substrate 11.

Sixth Embodiment

Referring to FIG. 10, the configuration of a display device 600according to a sixth embodiment will be explained. In view of thesimilarity between the first and sixth embodiments, the parts of thesixth embodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the sixthembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the sixth embodiment, unlike the first embodiment, the light emittingsubstrate 11 has a curved shape, while the luminance equalizer sheet 13has a flat shape. Specifically, in the illustrated embodiment, the lightemitting substrate 11 has a single curved shape. In particular, in theillustrated embodiment, the luminance equalizer sheet 13, which has alinear expansion coefficient smaller than a linear expansion coefficientof the light emitting substrate 11, has a flat shape, the light emittingsubstrate 11 has a curved shape that is convex toward the luminanceequalizer sheet 13, and the degree of curvature of the luminanceequalizer sheet 13 is configured to be smaller than the degree ofcurvature of the light emitting substrate 11. The bottom portion 161 ofthe holding member 16 has a curved shape that is convex toward the lightemitting substrate 11 in the cross section of the display device 600taken along the X direction. The diffusion member 14, the optical sheet15, a holding portion 163 h of the holding member 16, and the displaypanel 2 have a flat shape in the cross section of the display device 600taken along the X direction. The light emitting substrate 11 and theluminance equalizer sheet 13 are designed so that the light emittingsubstrate 11 is curved such that an angle θ6 between a tangent plane TP6a of the light emitting substrate 11 and a plane P6 of the luminanceequalizer sheet 13 in the perpendicular direction of the tangent planeTP6 a of the light emitting substrate 11 increases as moving away fromthe positioning position. Specifically, the light emitting substrate 11is curved with respect to the luminance equalizer sheet 13 so that theangle θ6 between the tangent plane TP6 a of the light emitting substrate11 at a position of the light emitting substrate 11 and the tangentplane TP6 b of the luminance equalizer sheet 13 at a position of theluminance equalizer sheet 13 located in the perpendicular direction ofthe tangent plane TP6 a of the light emitting substrate 11 relative tothe position of the light emitting substrate 11 increases as theposition of the light emitting substrate 11 moving away from thepositioning position. More specifically, in the illustrated embodiment,the angle θ6 monotonically increases as moving outward in the Xdirection relative to a longitudinal center plane of the display device600 that is a YZ plane and extends through the positioning positions ornotches of the light emitting substrate 11 and the luminance equalizersheet 13. In this embodiment, the materials of the luminance equalizersheet 13 and the light emitting substrate 11 are not particularlylimited as long as the linear expansion coefficient of the luminanceequalizer sheet 13 is smaller than the linear expansion coefficient ofthe light emitting substrate 11.

Also, in the sixth embodiment above, unlike the first embodiment abovewhich includes the curved holding portion 163 having the curved holdingportion 163 that is formed in a curved shape at the side portions 162along the X direction and is formed in a flat shape at the side portions162 along the Y direction, since the luminance equalizer sheet 13 has aflat shape, the holding member 16 includes the holding portion 163 hthat is formed in a flat shape at all side portions 162 along the Xdirection and the Y direction. The holding portion 163 h is similar tothe curved holding portion 163 in the first embodiment in itsconfiguration other than its shape.

The other configurations of the sixth embodiment are the same as thefirst embodiment above.

Effect of Sixth Embodiment

In the sixth embodiment, as described above, the luminance equalizersheet 13, which has the linear expansion coefficient smaller than thelinear expansion coefficient of the light emitting substrate 11, has aflat shape, the light emitting substrate 11 has a curved shape that isconvex toward the luminance equalizer sheet 13, and the degree ofcurvature of the luminance equalizer sheet 13 is configured to besmaller than the degree of curvature of the light emitting substrate 11.With this configuration, as in the first embodiment above, deteriorationof luminance uniformity caused by temperature changes can be suppressedby reducing misalignment of the relative positional relationship of thelight emitting substrate 11 and the luminance equalizer sheet 13 causedby temperature changes.

Other effects of the sixth embodiment are the same as those of the firstembodiment.

In the sixth embodiment, alternatively, the luminance equalizer sheet13, which has the linear expansion coefficient smaller than the linearexpansion coefficient of the light emitting substrate 11, can have aflat shape, and the light emitting substrate 11 can have a curved shapethat is concave away from the luminance equalizer sheet 13.

Seventh Embodiment

Referring to FIG. 11, the configuration of a display device 700according to a seventh embodiment will be explained. In view of thesimilarity between the first and seventh embodiments, the parts of theseventh embodiment that are similar or identical to the parts of thefirst embodiment will be given the same reference numerals as the partsof the first embodiment. Moreover, the descriptions of the parts of theseventh embodiment that are similar or identical to the parts of thefirst embodiment may be omitted for the sake of brevity.

In the seventh embodiment, unlike the first embodiment, the lightemitting substrate 11 and the luminance equalizer sheet 13 each have acurved shape. Specifically, in the illustrated embodiment, the lightemitting substrate 11 and the luminance equalizer sheet 13 each have asingle curved shape. In particular, in the illustrated embodiment, theluminance equalizer sheet 13, which has a linear expansion coefficientlarger than a linear expansion coefficient of the light emittingsubstrate 11, has a curved shape that is convex toward the lightemitting substrate 11, the light emitting substrate 11 has a curvedshape that is convex toward the luminance equalizer sheet 13, and thedegree of curvature of the luminance equalizer sheet 13 is configured tobe larger than the degree of curvature of the light emitting substrate11. The bottom portion 161 of the holding member 16 has a curved shapethat is convex toward the light emitting substrate 11 in the crosssection of the display device 700 taken along the X direction. The lightemitting substrate 11 and the luminance equalizer sheet 13 are curvedwith respect to each other such that an angle θ7 between a tangent planeTP7 a of the light emitting substrate 11 and a tangent plane TP7 b ofthe luminance equalizer sheet 13 in the perpendicular direction of thetangent plane TP7 a of the light emitting substrate 11 increases asmoving away from the positioning position. Specifically, the lightemitting substrate 11 and the luminance equalizer sheet 13 are curved sothat the angle θ7 between the tangent plane TP7 a of the light emittingsubstrate 11 at a position of the light emitting substrate 11 and thetangent plane TP7 b of the luminance equalizer sheet 13 at a position ofthe luminance equalizer sheet 13 located in the perpendicular directionof the tangent plane TP7 a of the light emitting substrate 11 relativeto the position of the light emitting substrate 11 increases as theposition of the light emitting substrate 11 moving away from thepositioning position. More specifically, in the illustrated embodiment,the angle θ7 monotonically increases as moving outward in the Xdirection relative to a longitudinal center plane of the display device700 that is a YZ plane and extends through the positioning positions ornotches of the light emitting substrate 11 and the luminance equalizersheet 13.

The other configurations of the seventh embodiment are the same as thefirst embodiment above.

Effect of Seventh Embodiment

In the seventh embodiment, as described above, the luminance equalizersheet 13, which has the linear expansion coefficient larger than thelinear expansion coefficient of the light emitting substrate 11, has acurved shape that is convex toward the light emitting substrate 11, thelight emitting substrate 11 has a curved shape that is convex toward theluminance equalizer sheet 13, and the degree of curvature of theluminance equalizer sheet 13 is configured to be larger than the degreeof curvature of the light emitting substrate 11. With thisconfiguration, as in the first embodiment above, deterioration ofluminance uniformity caused by temperature changes can be suppressed byreducing misalignment of the relative positional relationship of thelight emitting substrate 11 and the luminance equalizer sheet 13 causedby temperature changes.

The other effects of the seventh embodiment are the same as those of thefirst embodiment.

Eighth Embodiment

Referring to FIG. 12, the configuration of a display device according toan eighth embodiment will be explained. In view of the similaritybetween the first and eighth embodiments, the parts of the eighthembodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the eighthembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the eighth embodiment, unlike the first embodiment, the holdingmember 16 is configured to include a first holding member 16 a and asecond holding member 16 b that is provided on an inner peripheralsurface side of the first holding member 16 a. In other words, theholding member 16 of the first embodiment is integrally formed as aone-piece, unitary member, for example, while the holding member 16 ofthe eighth embodiment includes the first and second holding members 16 aand 16 b that are independently formed as separate members.

The first holding member 16 a in the eighth embodiment has the sameconfiguration as the holding member 16 of the first embodiment, exceptthat the luminance equalizer sheet engaging protrusions 165 are notprovided. The first holding member 16 a is a box shape with an openingon the front surface side and has a bottom portion 161 a and four sideportions 162 a. The side portions 162 a have a first curved holdingportion 163 a and a plurality of (only one is shown in FIG. 13) lightemitting substrate engaging protrusions 164 a. The first curved holdingportion 163 a holds a recess portion 166 of the second holding member 16b, described later. The first curved holding portion 163 a forms a stepthat protrudes inward on the side portions 162 a. The light emittingsubstrate engaging protrusions 164 a position and fix the light emittingsubstrate 11 as in the first embodiment, and also engage with notches167 of the second holding member 16 b, described later, to position andfix the second holding member 16 b.

The second holding member 16 b has a tubular shape with openings on thefront surface side and the rear surface side, and has four side portions162 b. The second holding member 16 b is provided on the innerperipheral surface side of the first holding member 16 a. The secondholding member 16 b has a second curved holding portion 163 b protrudinginward on the side portions 162 b. The second curved holding portion 163b forms a step that supports the periphery of the luminance equalizersheet 13 and holds the curved shape of the luminance equalizer sheet 13,similar to the curved holding portion 163 of the first embodiment. Thesecond curved holding portion 163 b has a plurality of notches 167 thatengage with the light emitting substrate engaging protrusions 164 a ofthe first holding member 16 a, respectively, and a plurality of (onlyone is shown in FIG. 13) luminance equalizer sheet engaging protrusions165 b that engage with the notches of the luminance equalizer sheet 13,respectively. The recess portion 166 is formed on the outer peripheralside of the second holding member 16 b corresponding to the secondcurved holding portion 163 b, and the recess portion 166 is held incontact with the first curved holding portion 163 a. The second holdingmember 16 b is made of a material with a higher reflectivity than thefirst holding member 16 a, such as a white resin.

The other configurations of the eighth embodiment are the same as thefirst embodiment above.

Effect of Eighth Embodiment

In the eighth embodiment, as described above, the holding member 16includes the first holding member 16 a and the second holding member 16b that is provided on the inner peripheral surface side of the firstholding member 16 a and is made of a material with a higher reflectivitythan the first holding member 16 a. With this configuration, the lightutilization efficiency can be improved by reflecting the light on theside portions 162 b of the second holding member 16 b, and thus theluminance of the light emitting device 1 can be improved.

The other effects of the eighth embodiment are the same as those of thefirst embodiment.

Ninth Embodiment

Referring to FIGS. 13 and 14, the configuration of a display deviceaccording to a ninth embodiment will be explained. In view of thesimilarity between the first and ninth embodiments, the parts of theninth embodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the ninthembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the ninth embodiment, unlike the eighth embodiment, the holdingmember 16 includes the first holding member 16 a and a second holdingmember 16 c that is provided on an inner peripheral surface side of thefirst holding member 16 a. The second holding member 16 c of the ninthembodiment is identical to the second holding member 16 b of the eighthembodiment, expect that a grid-shaped planar member 168 c is provided inthe opening of the second holding member 16 c on the light emittingsubstrate 11 side. At the intersections of this grid, a plurality ofcolumnar members 169 are formed that contact a surface of the luminanceequalizer sheet 13 on the light emitting substrate 11 side. Thegrid-shaped planar member 168 c is formed so that the light emittingelements 111 on the light emitting substrate 11 are disposed in gapportions of the grid, respectively. In this embodiment, one columnarmember 169 is formed in each of four central intersections of theplurality of the intersections of the grid, but the location and numberof columnar members 169 are not particularly limited. In the illustratedembodiment, the grid-shaped planar member 168 c has a dimension (orheight) in the Z direction that is smaller than a dimension (or height)of the light emitting elements 111 in the Z direction and is smallerthan a distance between the surface of the luminance equalizer sheet 13on the light emitting substrate 11 side and a light reflection sidesurface of the reflective sheet 12. However, the grid-shaped planarmember 168 c can have a dimension (or height) in the Z direction that islarger than a dimension (or height) of the light emitting elements 111in the Z direction and is smaller than the distance between the surfaceof the luminance equalizer sheet 13 on the light emitting substrate 11side and the light reflection side surface of the reflective sheet 12.Thus, a front or top surface of the grid-shaped planar member 168 c isspaced apart from the surface of the luminance equalizer sheet 13 on thelight emitting substrate 11 side such that the front or top surface ofthe grid-shaped planar member 168 c does not directly contact with thesurface of the luminance equalizer sheet 13 on the light emittingsubstrate 11 side.

The other configuration of the ninth embodiment is the same as theeighth embodiment above.

Effect of Ninth Embodiment

In the ninth embodiment, as described above, the second holding member16 c has the columnar members 169 that contact the surface of theluminance equalizer sheet 13 on the light emitting substrate 11 side.With this configuration, the luminance equalizer sheet 13 can beprevented from bending toward the light emitting substrate 11 due to itsown weight.

The other effects of the ninth embodiment are the same as those of theeighth embodiment.

Tenth Embodiment

Referring to FIGS. 15 and 16, the configuration of a display deviceaccording to a tenth embodiment will be explained. In view of thesimilarity between the first and tenth embodiments, the parts of thetenth embodiment that are similar or identical to the parts of the firstembodiment will be given the same reference numerals as the parts of thefirst embodiment. Moreover, the descriptions of the parts of the tenthembodiment that are similar or identical to the parts of the firstembodiment may be omitted for the sake of brevity.

In the tenth embodiment, unlike the eighth embodiment, the holdingmember 16 includes the first holding member 16 a and a second holdingmember 16 d that is provided on an inner peripheral surface side of thefirst holding member 16 a. The second holding member 16 d of the tenthembodiment is identical to the second holding member 16 b of the eighthembodiment, expect that a grid-shaped partition wall 168 d is providedin the opening of the second holding member 16 d on the light emittingsubstrate 11 side. The grid-shaped partition wall 168 d partitions eachof the light emitting elements 111 and contacts a surface of theluminance equalizer sheet 13 on the light emitting substrate 11 side. Inthe illustrated embodiment, the grid-shaped partition wall 168 d has adimension (or height) in the Z direction that is larger than a dimension(or height) of the light emitting elements 111 in the Z direction and isequal to a distance between the surface of the luminance equalizer sheet13 on the light emitting substrate 11 side and a light reflection sidesurface of the reflective sheet 12. Thus, a surface of the grid-shapedpartition wall 168 d on the luminance equalizer sheet 13 side contactsthe luminance equalizer sheet 13, while a surface of the grid-shapedpartition wall 168 d on the light emitting substrate 11 side contactsthe light reflection side surface of the reflective sheet 12.

The other configurations of the tenth embodiment are the same as theeighth embodiment above.

Effect of Tenth Embodiment

In the tenth embodiment, as described above, the second holding member16 d has the grid-shaped partition wall 168 d that partitions each ofthe light emitting elements 111 and contacts the surface of theluminance equalizer sheet 13 on the light emitting substrate 11 side.With this configuration, partial dimming process called local dimmingcan be performed while preventing the luminance equalizer sheet 13 frombending toward the light emitting substrate 11 due to its own weight.

The other effects of the tenth embodiment are the same as those of theeighth embodiment.

MODIFICATION EXAMPLES

The embodiments disclosed here are illustrative and are not restrictivein all respects. The scope of the invention is indicated by the claimsrather than by the description of the embodiments described above, andfurthermore includes all modifications (modification examples) withinthe meaning and scope of the claims and their equivalents.

For example, in the first embodiment above, an example is shown in whichthe luminance equalizer sheet 13 has a curved shape or single curvedshape that is convex toward the light emitting substrate 11, but thepresent invention is not limited to this. At least the one with thelarger linear expansion coefficient among the light emitting substrate11 and the luminance equalizer sheet 13 can have a double curved shape.Specifically, the luminance equalizer sheet 13 can have a curved crosssectional shape in both cross sections of the display device 100 takenalong the X direction or a ZX plane and along the Y direction or a YZplane. In particular, At least the one with the larger linear expansioncoefficient among the light emitting substrate 11 and the luminanceequalizer sheet 13 can have a dome shape that is convex toward orconcave away from the one with the smaller linear expansion coefficient,and the degree of curvature of the one with the larger linear expansioncoefficient can be configured to be larger than the degree of curvatureof the one with the smaller linear expansion coefficient. For example,the luminance equalizer sheet 13, which has the linear expansioncoefficient larger than the linear expansion coefficient of the lightemitting substrate 11, can have a dome shape that is convex toward orconcave away from the light emitting substrate 11, the light emittingsubstrate 11 can have a flat shape, and the degree of curvature of theluminance equalizer sheet 13 can be configured to be larger than thedegree of curvature of the light emitting substrate 11. Even with thisconfiguration, the same effects as those of the first to tenthembodiments can be obtained in the curved portion of the one with thelarger linear expansion coefficient. Of course, the light emittingsubstrate 11 and the luminance equalizer sheet 13 each can have a doublecurved shape. Furthermore, in the second to fifth and seventhembodiments above, examples are shown in which the light emittingsubstrate 11 and the luminance equalizer sheet 13 each have a curvedshape or single curved shape, but the present invention is not limitedto this. For example, only one of the light emitting substrate 11 andthe luminance equalizer sheet 13 can have a single curved shape, whilethe other one of the light emitting substrate 11 and the luminanceequalizer sheet 13 can have a double curved shape or dome shape.Moreover, in the sixth embodiment, an example is show in which the lightemitting substrate 11 has a single curved shape, while the luminanceequalizer sheet 13 has a flat shape, but the present invention is notlimited to this. For example, the light emitting substrate 11 can have adouble curved shape, while the luminance equalizer sheet 13 has a flatshape.

For example, in the first embodiment above, an example is shown in whichthe luminance equalizer sheet 13 has a curved shape that is convextoward the light emitting substrate 11, but the present invention is notlimited to this. For example, the luminance equalizer sheet 13 can havea curved shape that is convex toward the light emitting substrate 11 andfurther have a flat shape that is connected to one end of this curvedportion. Even with this configuration, the same effects as those of thefirst to tenth embodiments can be obtained in the curved portion of theluminance equalizer sheet 13. The positioning positions of the lightemitting substrate 11 and the luminance equalizer sheet 13 can beprovided at the center portion of the holding member 16 in the Xdirection, or at a position away from the center portion of the holdingmember 16 in the X direction.

For example, the degree of curvature of the luminance equalizer sheet 13can be asymmetrical in the X direction with respect to the positioningpositions. Even with this configuration, the same effects as those ofthe first to tenth embodiments can be obtained. The positioningpositions of the light emitting substrate 11 and the luminance equalizersheet 13 can be provided at the center portions of the holding member 16in the X direction, or at positions away from the center portions of theholding member 16 in the X direction. When the luminance equalizer sheet13, which has the linear expansion coefficient larger than the linearexpansion coefficient of the light emitting substrate 11, has a domeshape that is convex toward or concave away from the light emittingsubstrate 11, the light emitting substrate 11 has a flat shape, and thepositioning positions of the light emitting substrate 11 and theluminance equalizer sheet 13 are provided at positions away from thecenter portions of the holding member 16 in the X direction, the shapeof the luminance equalizer sheet 13 can be a semioval shape.

For example, in the first embodiment above, an example is shown in whichthe holding member 16 has the light emitting substrate engagingprotrusions 164 and the luminance equalizer sheet engaging protrusions165, the light emitting substrate 11 has the notches that engage withthe light emitting substrate engaging protrusions 164, and the luminanceequalizer sheet 13 has the notches that engage with the luminanceequalizer sheet engaging protrusions 165, but the present invention isnot limited to this. As long as the light emitting substrate 11 andluminance equalizer sheet 13 can be fixed to be relatively positionedvia the holding member 16, the configuration of these engagements is notparticularly limited.

For example, in the first embodiment above, an example is shown in whichthe light emitting substrate 11 and the luminance equalizer sheet 13have a rectangular shape including four sides in plan view, but thepresent invention is not limited to this. For example, each part of thelight emitting device 1 (the light emitting substrate 11, the reflectivesheet 12, the luminance equalizer sheet 13, the diffusion member 14, theoptical sheet 15 and the holding member 16) can be formed in a shapecorresponding to the shape of the display panel 2, and can be circular,elliptical, polygonal, irregularly shaped (a shape including a concaveor convex portion, for example), other than rectangular.

For example, in the first embodiment above, an example is shown in whichthe bottom portion 161 of the holding member 16 has three light emittingsubstrate engaging protrusions 164 that protrude inward from the sideportions 162 along the X direction and the side portion 162 along the Ydirection, but the present invention is not limited to this. The numberof the light emitting substrate engaging protrusion 164 can be more thanor less than three. For example, the bottom portion 161 of the holdingmember 16 can have only one light emitting substrate engaging protrusion164 that protrudes inward from one side portion 162 along the Xdirection, or only two light emitting substrate engaging protrusion 164that protrude inward from the side portions 162 along the X direction,respectively.

For example, in the first embodiment above, an example is shown in whichthe curved holding portion 163 of the holding member 16 has threeluminance equalizer sheet engaging protrusions 165 that protrude inwardfrom the side portions 162 along the X direction and the side portion162 along the Y direction, but the present invention is not limited tothis. The number of the luminance equalizer sheet engaging protrusion165 can be more than or less than three. For example, the curved holdingportion 163 of the holding member 16 can have only one luminanceequalizer sheet engaging protrusion 165 that protrudes inward from oneside portion 162 along the X direction, or only two luminance equalizersheet engaging protrusion 165 that protrude inward from the sideportions 162 along the X direction.

(1) In view of the state of the known technology and in accordance witha first aspect of the present invention, a light emitting deviceaccording to the first aspect comprises a light emitting substrate witha plurality of light emitting elements, and a luminance equalizer sheetprovided opposite the light emitting substrate, having a plurality ofthrough holes for transmitting light irradiated from the light emittingelements and having a linear expansion coefficient different from alinear expansion coefficient of the light emitting substrate, the lightemitting substrate and the luminance equalizer sheet being positionedrelative to each other at a predetermined position, at least one with alarger linear expansion coefficient among the light emitting substrateand the luminance equalizer sheet having a curved shape, and a degree ofcurvature of the one with the larger linear expansion coefficient beinglarger than a degree of curvature of one with a smaller linear expansioncoefficient. Here, “a degree of curvature being small” of the presentdisclosure is a concept that includes not only being curved and havingsmall amount of curvature, but also being a non-curved flat surface.

The luminance equalizer sheet faces the principal surface of the lightemitting substrate on which the plurality of light emitting elements isarranged. In a preferable embodiment, the curved shape of the luminanceequalizer sheet is a non-curved flat shape, convex toward the lightemitting substrate or is concave away from the light emitting substrate.In another preferable embodiment, the curved shape of the light emittingsubstrate is a non-curved flat shape, convex toward the luminanceequalizer sheet, or concave away from the luminance equalizer sheet. Theabove-mentioned preferable embodiments can be combined so that at leastone of the luminance equalizer sheet and the light emitting substratehas the curved form which is convex or concave. In accordance withanother preferred embodiment of any one of the light emitting devicesmentioned above: the luminance equalizer sheet and the light emittingsubstrate primarily extend along a first axis and a second axis, andintersect a third axis which is perpendicular to the first and secondaxes; and the curved shape of the luminance equalizer sheet and thelight emitting substrate lies within a cross-sectional view whichextends along the first and the third axes. In accordance with anotherpreferred embodiment of any one of the light emitting devices mentionedabove, the predetermined position is located at a center position withrespect to the first axis. In accordance with another preferredembodiment of any one of the light emitting devices mentioned above: atleast one of the light emitting substrate and the luminance equalizersheet is curved within the plane extending along the first and thirdaxes such that an angle between a tangent plane or a plane of the lightemitting substrate and a tangent plane or a plane of the luminanceequalizer sheet increases as moving away along the first axis from thepredetermined position, the tangent plane or the plane of the luminanceequalizer sheet is a tangent plane identified on a line where theluminance equalizer sheet intersects another plane perpendicular to thetangent plane or the plane of the light emitting substrate.

In the light emitting device according to the first aspect, as describedabove, at least the one with the larger linear expansion coefficientamong the light emitting substrate and the luminance equalizer sheet hasthe curved shape, and the degree of curvature of the one with the largerlinear expansion coefficient is larger than the degree of curvature ofthe one with the smaller linear expansion coefficient. By making the onewith the larger linear expansion coefficient more curved, a positionalshift amount of the one with the larger linear expansion coefficientrelative to the one with the smaller linear expansion coefficient can bereduced at a position away from the predetermined position. In otherwords, if a positional shift direction caused by the expansion of theone with the smaller linear expansion coefficient is a referencedirection, then the one with the larger linear expansion coefficientexpands in a direction that is inclined relative to the referencedirection due to the curvature. As a result, the expansion of the onewith the larger linear expansion coefficient includes an orthogonaldirection component in a direction orthogonal to the referencedirection, in addition to a reference direction component correspondingto the positional shift. The positional shift (the reference directioncomponent) can be reduced by the amount of this orthogonal directioncomponent caused by the curvature. With this configuration,deterioration of luminance uniformity caused by temperature changes canbe suppressed by reducing misalignment of the relative positionalrelationship of the light emitting substrate and the luminance equalizersheet caused by temperature changes.

(2) In accordance with a preferred embodiment according to the lightemitting device mentioned above, at least one of the light emittingsubstrate and the luminance equalizer sheet is curved such that an anglebetween a tangent plane or a plane of the light emitting substrate and atangent plane or a plane of the luminance equalizer sheet in aperpendicular direction of the tangent plane or the plane of the lightemitting substrate increases as moving away from the predeterminedposition. Here, the farther away from the predetermined position, thelarger the positional shift amount due to expansion. Therefore, with theconfiguration above, the amount of the orthogonal direction componentgenerated in the one with the larger linear expansion coefficient can beincreased as moving away from the predetermined position, and thus anamount of decrease in the reference direction component can be increasedas moving away from the predetermined position. With this configuration,deterioration of luminance uniformity caused by temperature changes canbe further suppressed by further reducing misalignment of the relativepositional relationship of the light emitting substrate and theluminance equalizer sheet caused by temperature changes.

(3) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the predetermined positionis located on a plane on which a plane orthogonal to a tangent plane ofthe one with the larger linear expansion coefficient overlaps a planeorthogonal to a tangent plane or a plane of the one with the smallerlinear expansion coefficient. With this configuration, since the lightemitting substrate and luminance equalizer sheet, at least one of whichis curved, can be stably fixed at the predetermined position, theassemblability of the luminance equalizer sheet can be improved.

(4) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the linear expansioncoefficient of the luminance equalizer sheet is larger than the linearexpansion coefficient of the light emitting substrate, the luminanceequalizer sheet has a curved shape that is convex toward the lightemitting substrate or a curved shape that is concave away from the lightemitting substrate, and the light emitting substrate has a flat shape, acurved shape that has a smaller degree of curvature than the luminanceequalizer sheet and is convex toward the luminance equalizer sheet, or acurved shape that has a smaller degree of curvature than the luminanceequalizer sheet and is concave away from the luminance equalizer sheet.With this configuration, even if the luminance equalizer sheet has acurved shape and the light emitting substrate has a flat shape or acurved shape, the positional shift amount of the luminance equalizersheet, which has a larger linear expansion coefficient, with respect tothe light emitting substrate, which has a smaller linear expansioncoefficient, can be reduced at a position away from the predeterminedposition. As a result, the deterioration of luminance uniformity can besuppressed.

(5) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the linear expansioncoefficient of the luminance equalizer sheet is smaller than the linearexpansion coefficient of the light emitting substrate, the luminanceequalizer sheet has a flat shape, a curved shape that is convex towardthe light emitting substrate, or a curved shape that is concave awayfrom the light emitting substrate, and the light emitting substrate hasa curved shape that has a larger degree of curvature than the luminanceequalizer sheet and is convex toward the luminance equalizer sheet, or acurved shape that has a larger degree of curvature than the luminanceequalizer sheet and is concave away from the luminance equalizer sheet.With this configuration, even if the luminance equalizer sheet has aflat shape or a curved shape and the light emitting substrate has acurved shape, the positional shift amount of the light emittingsubstrate, which has a larger linear expansion coefficient, with respectto the luminance equalizer sheet, which has a smaller linear expansioncoefficient, can be reduced at a position away from the predeterminedposition. As a result, the deterioration of luminance uniformity can besuppressed.

(6) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, in the configuration inwhich the linear expansion coefficient of the luminance equalizer sheetis larger than the linear expansion coefficient of the light emittingsubstrate and the degree of curvature of the luminance equalizer sheetis larger than the degree of curvature of the light emitting substrate,or the configuration in which the linear expansion coefficient of theluminance equalizer sheet is smaller than the linear expansioncoefficient of the light emitting substrate and the degree of curvatureof the luminance equalizer sheet is smaller than the degree of curvatureof the light emitting substrate above, the light emitting device furthercomprises a diffusion member disposed on an opposite side of theluminance equalizer sheet from the light emitting substrate and having acurved shape corresponding to the curved shape of the luminanceequalizer sheet. With this configuration, the degree of curvature of theluminance equalizer sheet, which has a curved shape, can beappropriately maintained by the diffusion member. As a result, thedeterioration of luminance uniformity caused by temperature changes canbe suppressed.

(7) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the light emitting devicefurther comprises an optical sheet disposed on an opposite side of thediffusion member from the luminance equalizer sheet and has a curvedshape corresponding to the curved shape of the luminance equalizersheet. With this configuration, the degree of curvature of the luminanceequalizer sheet, which has a curved shape, can be more appropriatelymaintained. Therefore, the deterioration of luminance uniformity causedby temperature changes can be further suppressed.

(8) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the light emitting devicefurther comprises a holding member holding the light emitting substrateand the luminance equalizer sheet.

(9) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the holding member includesa curved holding portion having a curved shape for holding curvature ofthe luminance equalizer sheet. With this configuration, a luminanceequalizer sheet with a desired curved shape can be configured simply byplacing a luminance equalizer sheet formed by a flexible sheet on thecurved holding portion.

(10) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the curved holding portionincludes an engaging protrusion that engages with the luminanceequalizer sheet.

(11) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the holding member includesa bottom portion on which the light emitting substrate is disposed.

(12) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the holding member includesa first holding member and a second holding member that is provided onan inner peripheral surface side of the first holding member and isformed of a material with a higher reflectivity than the first holdingmember. With this configuration, the light utilization efficiency can beimproved by reflecting the light with the second holding member. As aresult, the luminance of the light emitting device can be improved. Thefirst holding member has a tubular-like side portion and a bottomportion. The light emitting substrate is fixed to the first holdingmember. Preferably, the second holding member has a tubular-like shapewhich is configured to fit to the inner surface of the side portion ofthe first holding member. The second holding member is configured tohold the peripheral portion of the luminance equalizer sheet.

(13) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the second holding memberhas a columnar member that contacts a surface of the luminance equalizersheet on the light emitting substrate side. With this configuration, theluminance equalizer sheet can be prevented from bending toward the lightemitting substrate due to its own weight.

(14) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, in the configuration inwhich the holding member includes the first holding member and thesecond holding member above, the second holding member has a partitionwall that partitions each of the light emitting elements and contacts asurface of the luminance equalizer sheet on the light emitting substrateside. With this configuration, partial dimming process called localdimming can be performed while preventing the luminance equalizer sheetfrom bending toward the light emitting substrate due to its own weight.

(15) In view of the state of the known technology and in accordance witha second aspect of the present invention, a display device according tothe second aspect comprises any one of the light emitting devicesmentioned above, and a display panel, the luminance equalizer sheethaving a curved shape, and the display panel being disposed on theluminance equalizer sheet side of the light emitting device and having acurved shape that corresponds to the curved shape of the luminanceequalizer sheet.

In the display device according to the second aspect, as describedabove, at least the one with the larger linear expansion coefficientamong the light emitting substrate and the luminance equalizer sheet hasthe curved shape, and the degree of curvature of the one with the largerlinear expansion coefficient is larger than the degree of curvature ofthe one with the smaller linear expansion coefficient. By making the onewith the larger linear expansion coefficient more curved, a positionalshift amount of the one with the larger linear expansion coefficientrelative to the one with the smaller linear expansion coefficient can bereduced at a position away from the predetermined position. In otherwords, if a positional shift direction caused by the expansion of theone with the smaller linear expansion coefficient is a referencedirection, then the one with the larger linear expansion coefficientexpands in a direction that is inclined relative to the referencedirection due to the curvature. As a result, the expansion of the onewith the larger linear expansion coefficient includes an orthogonaldirection component in a direction orthogonal to the referencedirection, in addition to a reference direction component correspondingto the positional shift. The positional shift (the reference directioncomponent) can be reduced by the amount of this orthogonal directioncomponent caused by the curvature. With this configuration,deterioration of luminance uniformity caused by temperature changes canbe suppressed by reducing misalignment of the relative positionalrelationship of the light emitting substrate and the luminance equalizersheet caused by temperature changes.

(16) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the curved shape of theleast one with the larger linear expansion coefficient among the lightemitting substrate and the luminance equalizer sheet is a single curvedshape.

(17) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the curved shape of theleast one with the larger linear expansion coefficient among the lightemitting substrate and the luminance equalizer sheet is a double curvedshape.

(18) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the bottom portion has aflat shape for holding the light emitting substrate.

(19) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the bottom portion has acurved shape for holding curvature of the light emitting substrate.

(20) In accordance with a preferred embodiment according to any one ofthe light emitting devices mentioned above, the second holding memberhas a grid-shaped planar member that partitions each of the lightemitting elements and is spaced apart from a surface of the luminanceequalizer sheet on the light emitting substrate side.

With the present disclosure, as described above, a light emitting deviceand a display device can be provided that can suppress deterioration ofluminance uniformity caused by temperature changes by reducingmisalignment of the relative positional relationship of the lightemitting substrate and the luminance equalizer sheet caused bytemperature changes.

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts unless otherwise stated.

As used herein, the following directional terms “forward”, “rearward”,“front”, “rear”, “up”, “down”, “above”, “below”, “upward”, “downward”,“top”, “bottom”, “side”, “vertical”, “horizontal”, “perpendicular” and“transverse” as well as any other similar directional terms refer tothose directions of a display device in an upright position.Accordingly, these directional terms, as utilized to describe thedisplay device should be interpreted relative to a display device in anupright position. The terms “left” and “right” are used to indicate the“right” when referencing from the right side as viewed from the front ofthe display device, and the “left” when referencing from the left sideas viewed from the front of the display device.

Also it will be understood that although the terms “first” and “second”may be used herein to describe various components these componentsshould not be limited by these terms. These terms are only used todistinguish one component from another. Thus, for example, a firstcomponent discussed above could be termed a second component andvice-a-versa without departing from the teachings of the presentinvention. The term “attached” or “attaching”, as used herein,encompasses configurations in which an element is directly secured toanother element by affixing the element directly to the other element;configurations in which the element is indirectly secured to the otherelement by affixing the element to the intermediate member(s) which inturn are affixed to the other element; and configurations in which oneelement is integral with another element, i.e. one element isessentially part of the other element. This definition also applies towords of similar meaning, for example, “joined”, “connected”, “coupled”,“mounted”, “bonded”, “fixed” and their derivatives. Finally, terms ofdegree such as “substantially”, “about” and “approximately” as usedherein mean an amount of deviation of the modified term such that theend result is not significantly changed.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. For example, unless specifically stated otherwise,the size, shape, location or orientation of the various components canbe changed as needed and/or desired so long as the changes do notsubstantially affect their intended function. Unless specifically statedotherwise, components that are shown directly connected or contactingeach other can have intermediate structures disposed between them solong as the changes do not substantially affect their intended function.The functions of one element can be performed by two, and vice versaunless specifically stated otherwise. The structures and functions ofone embodiment can be adopted in another embodiment. It is not necessaryfor all advantages to be present in a particular embodiment at the sametime. Every feature which is unique from the prior art, alone or incombination with other features, also should be considered a separatedescription of further inventions by the applicant, including thestructural and/or functional concepts embodied by such feature(s). Thus,the foregoing descriptions of the embodiments according to the presentinvention are provided for illustration only, and not for the purpose oflimiting the invention as defined by the appended claims and theirequivalents.

What is claimed is:
 1. A light emitting device comprising: a lightemitting substrate with a plurality of light emitting elements; and aluminance equalizer sheet provided opposite the light emittingsubstrate, having a plurality of through holes for transmitting lightirradiated from the light emitting elements and having a linearexpansion coefficient different from a linear expansion coefficient ofthe light emitting substrate, the light emitting substrate and theluminance equalizer sheet being positioned relative to each other at apredetermined position, at least one with a larger linear expansioncoefficient among the light emitting substrate and the luminanceequalizer sheet having a curved shape, and a degree of curvature of theone with the larger linear expansion coefficient being larger than adegree of curvature of one with a smaller linear expansion coefficientamong the light emitting substrate and the luminance equalizer sheet. 2.The light emitting device according to claim 1, wherein at least one ofthe light emitting substrate and the luminance equalizer sheet is curvedsuch that an angle between a tangent plane or a plane of the lightemitting substrate and a tangent plane or a plane of the luminanceequalizer sheet in a perpendicular direction of the tangent plane or theplane of the light emitting substrate increases as moving away from thepredetermined position.
 3. The light emitting device according to claim1, wherein the predetermined position is located on a plane on which aplane orthogonal to a tangent plane of the one with the larger linearexpansion coefficient overlaps a plane orthogonal to a tangent plane ora plane of the one with the smaller linear expansion coefficient.
 4. Thelight emitting device according to claim 1, wherein the linear expansioncoefficient of the luminance equalizer sheet is larger than the linearexpansion coefficient of the light emitting substrate, the luminanceequalizer sheet has a curved shape that is convex toward the lightemitting substrate or a curved shape that is concave away from the lightemitting substrate, and the light emitting substrate has a flat shape, acurved shape that has a smaller degree of curvature than the luminanceequalizer sheet and is convex toward the luminance equalizer sheet, or acurved shape that has a smaller degree of curvature than the luminanceequalizer sheet and is concave away from the luminance equalizer sheet.5. The light emitting device according to claim 4, further comprising adiffusion member disposed on an opposite side of the luminance equalizersheet from the light emitting substrate and having a curved shapecorresponding to the curved shape of the luminance equalizer sheet. 6.The light emitting device according to claim 5, further comprising anoptical sheet disposed on an opposite side of the diffusion member fromthe luminance equalizer sheet and having a curved shape corresponding tothe curved shape of the luminance equalizer sheet.
 7. The light emittingdevice according to claim 1, wherein the linear expansion coefficient ofthe luminance equalizer sheet is smaller than the linear expansioncoefficient of the light emitting substrate, the luminance equalizersheet has a flat shape, a curved shape that is convex toward the lightemitting substrate, or a curved shape that is concave away from thelight emitting substrate, and the light emitting substrate has a curvedshape that has a larger degree of curvature than the luminance equalizersheet and is convex toward the luminance equalizer sheet, or a curvedshape that has a larger degree of curvature than the luminance equalizersheet and is concave away from the luminance equalizer sheet.
 8. Thelight emitting device according to claim 1, further comprising a holdingmember holding the light emitting substrate and the luminance equalizersheet.
 9. The light emitting device according to claim 8, wherein theholding member includes a curved holding portion having a curved shapefor holding curvature of the luminance equalizer sheet.
 10. The lightemitting device according to claim 9, wherein the curved holding portionincludes an engaging protrusion that engages with the luminanceequalizer sheet.
 11. The light emitting device according to claim 8,wherein the holding member includes a bottom portion on which the lightemitting substrate is disposed.
 12. The light emitting device accordingto claim 11, wherein the bottom portion has a flat shape for holding thelight emitting substrate.
 13. The light emitting device according toclaim 11, wherein the bottom portion has a curved shape for holdingcurvature of the light emitting substrate.
 14. The light emitting deviceaccording to claim 8, wherein the holding member includes a firstholding member and a second holding member that is provided on an innerperipheral surface side of the first holding member and is formed of amaterial with a higher reflectivity than the first holding member. 15.The light emitting device according to claim 14, wherein the secondholding member has a columnar member that contacts a surface of theluminance equalizer sheet on the light emitting substrate side.
 16. Thelight emitting device according to claim 14, wherein the second holdingmember has a partition wall that partitions each of the light emittingelements and contacts a surface of the luminance equalizer sheet on thelight emitting substrate side.
 17. The light emitting device accordingto claim 14, wherein the second holding member has a grid-shaped planarmember that partitions each of the light emitting elements and is spacedapart from a surface of the luminance equalizer sheet on the lightemitting substrate side.
 18. A display device comprising: the lightemitting device according to claim 1; and a display panel, the luminanceequalizer sheet having a curved shape, and the display panel beingdisposed on the luminance equalizer sheet side of the light emittingdevice and having a curved shape that corresponds to the curved shape ofthe luminance equalizer sheet.
 19. The light emitting device accordingto claim 1, wherein the curved shape of the one with the larger linearexpansion coefficient among the light emitting substrate and theluminance equalizer sheet is a single curved shape.
 20. The lightemitting device according to claim 1, wherein the curved shape of theleast one with the larger linear expansion coefficient among the lightemitting substrate and the luminance equalizer sheet is a double curvedshape.